Dr. Stephen Olsen

Seoul National University, Korea
Email: solsen.at.hep1.snu.ac.kr
Feb. 2011

I have been doing charmonium- and bottomonium-related experiments since 1978 when I was a member of the original CLEO team. Since then I have continued similar lines of research at the TRISTAN and KEKB e⁺e^- colliders in Japan, as part of the AMY and, later, Belle experiments, and the BEPC e⁺e^- collider in Beijing as part of the BES experiments. My main interest has been the spectroscopy of mesons comprised of charmed-anticharmed quark pairs and their counterparts in the bottom-quark sector, and searches for more exotic structures such as four-quark mesons and possible meson-antimeson bound molecule-like particles.

The Belle experiment at KEKB was designed to make comprehensive studies of CP violations (matter-antimatter asymmetries) in the decays of B mesons (i.e. mesons that contain a bottom quark). This program was quite successful and large CP violations have been observed in many B meson decay modes. As an unexpected bonus, the data collected by the Belle detector has been used to discover previously unseen charmonium and bottomonium mesons and a number of possible multi-quark states such as the X(3872), Y(3940) and Z(4430). In addition to reviewing the history of charmonium & bottomonium research I will describe recent results on the X, Y & Z mesons, and the status of their theoretical understanding.

Do you want to know more?

• [1] "The Exotic XYZ Charmonium-like Mesons," Stephen Godfrey and Stephen L. Olsen Ann. Rev. Nucl and Part. Sci. 2008.58, 51-73, arXiv:0801.3867
• [2] "Observation of a narrow charmonium - like state in exclusive B+- ---> K+- pi+ pi- J / psi decays.," S.-K. Choi, S.L. Olsen et al., (Belle Collaboration), PRL 91, 262001 (2003), hep-ex/0309032.
• [3] "Observation of a near-threshold omega J/psi mass enhancement in exclusive B ---> K omega J/psi decays," S.-K. Choi, S.L. Olsen et al., (Belle Collaboration), PRL 94, 182002 (2005), hep-ex/0408126.
• [4] "Observation of a resonance-like structure in the pi+- psi-prime mass distribution in exclusive B ---> K pi+- psi-prime decays," S.-K. Choi, S.L. Olsen et al., (Belle Collaboration), PRL 100, 142001 (2008), arXiv:0708.1790.